Serial and Parallel Transmission
Parallel Transmission
In parallel transmission of data, all the bits of a byte are transmitted simultaneously on separate wires. Many wires (128, 64, 32) are used to send data signals simultaneously. Much more expensive, but much quicker. Used for short distances - less than a few metres. A greater distance results in crosstalk – the signals don’t arrive in the right order or at the correct time, as well as being more expensive.
| Advantages | Disadvantages |
| Much quicker because bits are sent at the same time. | Requires a separate cable for each bit sent per cycle. |
| Transmission in one clock cycle means clock frequency can be kept low without affecting the speed of the operation. | Unreliable over a long distance. |
Serial Transmission
In serial transmission, all the bits are transmitted serially one after the other on the same wire. Just requires one wire. Cheaper but slower, but practically possible over short and long distances. With fibre optic cables, very fast speeds can be obtained.
| Advantages | Disadvantages |
| One wire required. | Speed of data transfer low. |
| Reduced cost due to less number of conductors. | Clock frequency needs to be increased to increase the speed of data transfer. |